etcd (v3) store: implements KV methods of storage.Interface

pkg/runtime/helper.go

@@ -169,3 +169,13 @@ func (m MultiObjectTyper) IsUnversioned(obj Object) (bool, bool) {
 	}
 	return false, false
 }
+
+// SetZeroValue would set the object of objPtr to zero value of its type.
+func SetZeroValue(objPtr Object) error {
+	v, err := conversion.EnforcePtr(objPtr)
+	if err != nil {
+		return err
+	}
+	v.Set(reflect.Zero(v.Type()))
+	return nil
+}

pkg/storage/errors.go

@@ -26,6 +26,7 @@ const (
 	ErrCodeKeyNotFound int = iota + 1
 	ErrCodeKeyExists
 	ErrCodeResourceVersionConflicts
+	ErrCodeInvalidObj
 	ErrCodeUnreachable
 )
 
@@ -33,6 +34,7 @@ var errCodeToMessage = map[int]string{
 	ErrCodeKeyNotFound:              "key not found",
 	ErrCodeKeyExists:                "key exists",
 	ErrCodeResourceVersionConflicts: "resource version conflicts",
+	ErrCodeInvalidObj:               "invalid object",
 	ErrCodeUnreachable:              "server unreachable",
 }
 
@@ -68,15 +70,24 @@ func NewUnreachableError(key string, rv int64) *StorageError {
 	}
 }
 
+func NewInvalidObjError(key, msg string) *StorageError {
+	return &StorageError{
+		Code:               ErrCodeInvalidObj,
+		Key:                key,
+		AdditionalErrorMsg: msg,
+	}
+}
+
 type StorageError struct {
-	Code            int
-	Key             string
-	ResourceVersion int64
+	Code               int
+	Key                string
+	ResourceVersion    int64
+	AdditionalErrorMsg string
 }
 
 func (e *StorageError) Error() string {
-	return fmt.Sprintf("StorageError: %s, Code: %d, Key: %s, ResourceVersion: %d",
-		errCodeToMessage[e.Code], e.Code, e.Key, e.ResourceVersion)
+	return fmt.Sprintf("StorageError: %s, Code: %d, Key: %s, ResourceVersion: %d, AdditionalErrorMsg: %s",
+		errCodeToMessage[e.Code], e.Code, e.Key, e.ResourceVersion, e.AdditionalErrorMsg)
 }
 
 // IsNotFound returns true if and only if err is "key" not found error.
@@ -96,15 +107,24 @@ func IsUnreachable(err error) bool {
 
 // IsTestFailed returns true if and only if err is a write conflict.
 func IsTestFailed(err error) bool {
-	return isErrCode(err, ErrCodeResourceVersionConflicts)
+	return isErrCode(err, ErrCodeResourceVersionConflicts, ErrCodeInvalidObj)
+}
+
+// IsInvalidUID returns true if and only if err is invalid UID error
+func IsInvalidObj(err error) bool {
+	return isErrCode(err, ErrCodeInvalidObj)
 }
 
-func isErrCode(err error, code int) bool {
+func isErrCode(err error, codes ...int) bool {
 	if err == nil {
 		return false
 	}
 	if e, ok := err.(*StorageError); ok {
-		return e.Code == code
+		for _, code := range codes {
+			if e.Code == code {
+				return true
+			}
+		}
 	}
 	return false
 }

pkg/storage/interfaces.go

@@ -104,6 +104,7 @@ type Interface interface {
 	Set(ctx context.Context, key string, obj, out runtime.Object, ttl uint64) error
 
 	// Delete removes the specified key and returns the value that existed at that spot.
+	// If key didn't exist, it will return NotFound storage error.
 	Delete(ctx context.Context, key string, out runtime.Object, preconditions *Preconditions) error
 
 	// Watch begins watching the specified key. Events are decoded into API objects,
@@ -137,9 +138,13 @@ type Interface interface {
 
 	// GuaranteedUpdate keeps calling 'tryUpdate()' to update key 'key' (of type 'ptrToType')
 	// retrying the update until success if there is index conflict.
-	// Note that object passed to tryUpdate may change acress incovations of tryUpdate() if
-	// other writers are simultaneously updateing it, to tryUpdate() needs to take into account
+	// Note that object passed to tryUpdate may change across invocations of tryUpdate() if
+	// other writers are simultaneously updating it, to tryUpdate() needs to take into account
 	// the current contents of the object when deciding how the update object should look.
+	// If the key doesn't exist, it will return NotFound storage error if ignoreNotFound=false
+	// or zero value in 'ptrToType' parameter otherwise.
+	// If the object to update has the same value as previous, it won't do any update
+	// but will return the object in 'ptrToType' parameter.
 	//
 	// Example:
 	//